The present invention relates generally to fastener-driving tools, and more specifically to such tools operating under combustion power, also referred to as combustion tools or combustion nailers.
Combustion nailers are known in the art, and one type of such tools, also known as IMPULSE® brand tools for use in driving fasteners into workpieces, is described in commonly assigned patents to Nikolich U.S. Pat. Re. No. 32,452, and U.S. Pat. Nos. 4,522,162; 4,483,473; 4,483,474; 4,403,722; 5,197,646; 5,263,439 and 6,145,724, all of which are incorporated by reference herein. Similar combustion-powered nail and staple driving tools are available commercially from ITW-Paslode of Vernon Hills, Ill. under the IMPULSE®, BUILDEX® and PASLODE® brands.
Such tools are typically provided in a larger, higher powered “framing tool” type, and a smaller, lower powered “trim tool” type. While both types of tools operate according to very similar principles, the above-listed patents refer mainly to framing tools, and U.S. Pat. Nos. 6,176,412 and 6,012,622, both of which are incorporated by reference, disclose trim tools. Further, the conventional tools of both types include a tool housing enclosing a power source in the form of a small internal combustion engine. The engine is powered by a canister of pressurized fuel gas, also called a fuel cell. A battery-powered electronic power distribution unit produces a spark for ignition, and a fan located in a combustion chamber provides for both an efficient combustion within the chamber, while facilitating processes ancillary to the combustion operation of the device. The engine includes a reciprocating piston with an elongated, rigid driver blade disposed within a single cylinder body.
To drive a fastener, the operator presses the nosepiece of the tool against the workpiece, causing a workpiece contact element (WCE) to retract relative to the nosepiece. The WCE is connected via an upper probe to a cylindrical valve sleeve, which in part defines a combustion chamber. The retraction of the WCE causes the valve sleeve to close and seal the combustion chamber, which also causes a metered dose of fuel into the combustion chamber. This action also energizes a fan in the combustion chamber to begin circulation of the vaporized fuel.
Upon the pulling of a trigger switch, which causes the spark to ignite a charge of gas in the combustion chamber of the engine, the combined piston and driver blade is forced downward to impact a positioned fastener and drive it into the workpiece. The piston then returns to its original or pre-firing position through differential gas pressures within the cylinder. Fasteners are fed magazine-style into the nosepiece, where they are held in a properly positioned orientation for receiving the impact of the driver blade.
A valve sleeve is axially reciprocable about the cylinder and, through a linkage, moves to close the combustion chamber when a work contact element (WCE) at the end of the linkage is pressed against a workpiece. This pressing action also triggers a fuel-metering valve to introduce a specified volume of fuel into the closed combustion chamber.
Combustion-powered tools now offered on the market are sequentially operated tools. The tool must be pressed against the workpiece, retracting the WCE before the trigger is pulled for the tool to fire a nail. However, conventional combustion nailers tend to heat up quickly, which also causes tool energy degradation.
Thus, a common design parameter of combustion nailers is increasing tool efficiency and keeping the tool operating temperature within acceptable ranges Another design parameter of combustion tools is providing sufficient power for driving fasteners into hard or resistant substrates, such as residential siding, while maintaining a tool size and weight which is conducive to prolonged use in the field without causing undue operator fatigue.